Fluid conditioning arrangements

ABSTRACT

A fluid conditioning arrangement comprises a primary heat exchanger configured to cool and/or heat the fluid; a secondary heat exchanger configured to cool and/or heat the fluid; and a controller for operating said secondary heat exchanger when said primary heat exchanger fails to cool and/or heat the fluid at a predetermined acceptablelevel; wherein said primary heat exchanger is a phase change material (PCM) based heat exchanger.

FIELD OF THE INVENTION

The invention relates to fluid conditioning arrangements, phase changematerial (PCM) modules and/or components operated in conjunction withthese. The invention is of particular applicability to the use of PCMfor the ambient temperature control, for example within domestic andcommercial buildings.

BACKGROUND

Phase change materials use the latent heat property of material to storethermal energy and can be used in methods of controlling temperature.Phase change materials are either organic such as paraffin ornon-paraffin compounds, inorganic (salt hydrates and metallics) oreutectic (organic-organic, organic-inorganic, inorganic-inorganic).Typically, PCMs have a latent heat capacity at least ten times largerthan their specific heat capacity.

The following prior art documents are acknowledged: DE102007013779, U.S.Pat. No. 5,647,225, U.S. Pat. No. 7,124,594, U.S. Pat. No. 7,162,878,U.S. Pat. No. 5,255,526, U.S. Pat. No. 7,363,772, U.S. Pat. No.5,211,029, U.S. Pat. No. 4,916,916, U.S. Pat. No 5,647,225, U.S. Pat.No. 5,860,287, and U.S. Pat. No. 6,393,861.

One of the objects of the invention is to try to improve primarily PCMbased fluid conditioning arrangements in terms of performance andreliability.

BRIEF SUMMARY OF THE DISCLOSURE

In a first broad independent aspect, the invention provides a fluidconditioning arrangement comprising a primary heat exchanger configuredto cool and/or heat fluid; a secondary heat exchanger configured to cooland/or heat fluid; and a controller for operating said secondary heatexchanger when said primary heat exchanger fails to cool and/or heat thefluid at a predetermined acceptable level, (or the fluid fails to coolor heat the primary heat exchanger to an acceptable level), wherein saidprimary heat exchanger is a phase change material (PCM) based heatexchanger.

This configuration improves the overall performance of the system as itallows the PCM heat exchanger to do most of the work of cooling and/orheating for minimal energy usage, but provides a backup system toimprove performance and reliability when needed. For example, a PCM maybe selected which freezes/melts around room temperature (20-26 C). Inmany climates such as Northern Europe the night time temperatures fallbelow 20 C, even in summer. Therefore the PCM can be used to store coolenergy from the night to provide space cooling during the day. Becausethese cycles rely on natural fluctuations and the weather, on occasionthe night time temperatures may not be low enough to freeze or rechargethe PCM. In this situation, a back up or booster system can be used toprovide additional cooling during the night, because the temperature isalready lower at night the back up or booster system has to do less workthan if it was run during the day and has the advantage of using cheapernight time electricity. In this situation the backup booster may onlyneed to cool the night time air by the difference between the targettemperature and the actual night time temperature, for example if thetemperature needed to freeze the PCM is 18 C, and the night timetemperature is 20 C the booster only needs to provide an additional 2degrees of cooling.

In a second scenario the PCM based heat exchanger may be required toprovide cooling or heating. Because the latent heat store is finitethere may be occasions where the system is required to provide moreenergy than stored. If the primary heat exchanger cannot adequately heator cool the fluid then the secondary system can provide an additionalheating or cooling of the fluid. This allows a primarily PCM coolingand/or heating system to minimise energy usage and operate under normalconditions, but have the performance and reliability of a conventionalsystem by incorporating a booster or backup system. It allows thearrangement to operate over a wide variety of outside temperatureconditions. It also further improves the energy efficiency when comparedto conventional systems.

In a subsidiary aspect, said secondary heat exchanger is selected from:a vapour compression cycle based air conditioning system, a heat pump,an absorption chiller, a desiccant, an adsorption cooler or a heaterelement, for example an electrical heater element, an electrical panelheater, or infrared heater.

In a subsidiary aspect, the secondary heat exchanger incorporates aliquid store suitable for cryogenic cooling. This combination furtherreduces the energy requirements for the secondary heat exchanger. It isparticularly advantageous when the use of the secondary heat exchangeris relatively infrequent.

In a further subsidiary aspect, said secondary heat exchangerincorporates a single or multiple stage evaporative cooler. Thiscombination synergistically reduces the energy requirement for anachievable level of cooling, because an evaporative cooler can be moreeffective at night.

In a further subsidiary aspect, the evaporative cooler incorporates ahousing with an air intake; a corresponding air outlet; a liquid inlet;a corresponding liquid outlet; and a wicking surface. It can alsoimprove the heat exchange between an evaporative cooler and a PCM heatexchanger due to the benefits of a fluid based heat exchanger whencompared to an air based heat exchanger.

In a further subsidiary aspect, said secondary heat exchangerincorporates a Peltier cooler. This configuration is also particularlyadvantageous in that the secondary heat exchanger is only requiredinfrequently. It also lends itself to a particularly compact solution.In a further subsidiary aspect, said secondary heat exchanger exchangesheat with a liquid which then exchanges heat with the PCM of saidprimary heat exchanger. This configuration has the advantage of using aheat transfer fluid with a higher capacity than air. This kind of systemmay however still be used to provide fresh cooled air.

In a further subsidiary aspect, said primary heat exchanger incorporatesone or more units housing PCM; wherein said housing incorporates a PCMtank. This configuration simplifies the construction when compared tomultiple packs in a housing.

In a further subsidiary aspect, said tank incorporates insulated sidesand at least one side without insulation in order to enhance convectionthrough said side. This configuration is particularly advantageous inorder to release cooling/heating into a room. In a generalization ofthis aspect, the tank may comprise at least one side that, in use, facesthe space with which heat is to be exchanged, e.g. the room to be heatedor cooled, and this side may be uninsulated. The sides which do not facethe space with which heat is to be exchanged may be insulated.

In a further broad independent aspect, the invention provides a phasechange material (PCM) module comprising one or more PCM packs; a housingfor thermally insulating said number of PCM packs from a module'ssurrounding medium; said packs being in the form of a panel with anupper surface, a lower surface and relatively narrow lateral sides;wherein a plurality of troughs in at least either the upper or lowersurfaces of the panel are provided to allow fluid to flow through themodule for heat exchange with PCM. This configuration reduces the numberof components required in order to provide the spaces in a stack of PCMpacks, and maximises surface area and the energy storage density of theheat exchanger.

In a further broad independent aspect, the invention provides a phasechange material (PCM) module comprising a number of PCM monoliths ortubes; a housing for thermally insulating said number of PCM monolithsfrom a module's surrounding medium; and gaps being formed between astack of said monoliths or tubes in said module to allow fluid to flowthrough the module for heat exchange with the PCM. This configurationallows a stack of such monoliths or tubes to achieve improved heatexchange with a heat transfer fluid. It also provides a particularlyrobust stack which is also particularly straightforward to assemblewhilst employing relatively lightweight individual components.

In a further subsidiary aspect, said monoliths are hexagonal incross-section. This allows the individual monoliths to be stacked in auniform manner.

In a further broad independent aspect, the invention provides a phasechange material (PCM) module comprising a number of PCM packs; a housingfor thermally insulating said number of PCM packs from a module'ssurrounding medium; and conduits passing through said PCM packs to allowfluid to flow through the module for heat exchange with the PCM. Thisconfiguration further improves the efficiency of the heat exchange forcertain applications.

In a further broad independent aspect, the invention provides a fluidconditioning arrangement comprising a first heat exchanger configured toheat and/or cool fluid; and a second heat exchanger configured to cooland/or heat fluid; wherein said one of said heat exchangers is a phasechange material (PCM) based heat exchanger and the other is anevaporative cooler. This configuration is also particularly advantageousin terms of energy efficiency when compared to conventional heat pumpsand conventional combinations of heat pumps and evaporative coolers.

In a further broad independent aspect, the invention provides a fluidconditioning arrangement comprising a first heat exchanger configured tocool and/or heat fluid; and a second heat exchanger configured to cooland/or heat fluid; wherein said one of said heat exchangers is a phasechange material (PCM) based heat exchanger; and the other is a Peltiercooler. This configuration is also particularly advantageous in terms ofefficiency when compared to conventional combinations of heat pumps andPCM material. It lends itself to the Peltier acting as a booster systemwhich is particularly advantageous when the demand for the use of thePeltier cooler is relatively infrequent.

In a further broad independent aspect, the invention provides a fluidconditioning arrangement comprising a first heat exchanger configured tocool and/or heat fluid; and a second heat exchanger configured to cooland/or heat fluid; wherein said one of said heat exchangers is a phasechange material (PCM) based heat exchanger; and the other is a solarbased heat exchanger or solar collector.

In a further broad independent aspect, the invention provides atransportable PCM (phase change material) module comprising a number ofPCM packs; a housing for thermally insulting said number of PCM packsfrom a module's surrounding medium; spaces separating said packs andforming one or more channels for the flow of a fluid; said housingincorporating a fluid inlet and a fluid outlet; whereby, in use, fluidflows through said channels from said inlet to said outlet.

This configuration is particularly advantageous because it allowssystems to be built up from a number of modules for variable energyrequirement. It may also reverse conventional thinking when it isconfigured without any driven or powered component in the module. It maythus allow for retrofitting to existing air flow systems. It alsoimproves energy usage effectiveness.

In a subsidiary aspect, said inlet and/or said outlet incorporates oneor more flow regulating valves. If the module consists of thesecomponents only it further reduces the number of components necessaryand allows for particularly compact modules compared to moduleincorporating power components per module.

In a further subsidiary aspect, said PCM packs are arrangedsubstantially side by side. In this configuration, the cooling isadvantageous.

In a further subsidiary aspect, said PCM packs are separated by one ormore thermal conductors extending transversely and forming saidchannels. This allows the PCM portion to be of greater effective volumeand therefore improves its effectiveness.

Further aspects improve one or more of the following: the effectivenessof the PCM, the turbulence of the flow, the compactness of the systemrelative to its effectiveness, its overall packaging weight and itsmanufacturing requirements.

In a further subsidiary aspect, said thermal conductors take the form ofa corrugated sheet.

In a further subsidiary aspect, at least one of said PCM packincorporates a corrugated wall forming a channel for the flow of fluid.

In a further subsidiary aspect, a number of projections are provided inat least one of said channels.

In a further subsidiary aspect, at least one of said PCM packincorporates a wall from which projections project into said channel.

In a further subsidiary aspect, the or each PCM pack comprises alaminate of a first conducting panel and a second conducting panelenclosing a portion formed primarily of PCM; wherein said portion of PCMincorporates thermal conductors. In a further subsidiary aspect, saidthermal conductors extend in a transverse direction from one or both ofsaid conducting panels.

In a further subsidiary aspect, said thermal conductors form hexagonalcells when viewed in plan.

In a further subsidiary aspect, said laminate further incorporates acorrugated thermally conductive panel.

In a further subsidiary aspect, said laminate incorporates a thirdconductive panel and a fourth conductive panel enclosing a secondportion formed primarily of PCM; and a corrugated thermally conductivepanel located between said second and third conductive panels.

In a further subsidiary aspect, said laminate incorporates a pluralityof projections on said panels.

In a further subsidiary aspect, said thermally conductive panels areselected from the group comprising aluminium based material, steel basedmaterial, and plastics material.

In a further subsidiary aspect, said PCM is selected from the groupcomprising a salt, a salt based hydrate, a mixture of salt, and/or saltbased hydrate, and/or an organic material.

In a further subsidiary aspect, said salt based hydrate are selectedfrom the group comprising hydrated calcium chloride or hydrated sodiumsulphate.

In a further subsidiary aspect, said salt based hydrate incorporates athickening agent selected from the group comprising Xanthan and/orLaponite.

In a further subsidiary aspect, said organic material is paraffin based.

In a further subsidiary aspect, said thermal conductors incorporate aconductive compound mixed into said PCM. In a further subsidiary aspect,said thermal conductor is a carbon based compound mixed into said PCM.

In a further subsidiary aspect, said carbon based compound is carbonblack.

In a further subsidiary aspect, said thermal conductors incorporate wirewool or chemical carbon nanotubes.

In a further subsidiary aspect, said module further incorporates apettier cooler.

In a further subsidiary aspect, said module further incorporates anevaporative cooler.

In a second broad independent aspect, the invention provides an airconditioning arrangement, comprising:

-   -   one or more transportable PCM modules according to any of the        preceding claims; and    -   at least one transportable control module incorporating a        housing with an inlet and an outlet; and a pump for causing, in        use, the flow of fluid from said inlet to said outlet;    -   wherein said arrangement incorporates a conduit for linking said        transportable control module to said transportable PCM modules.

In a subsidiary aspect, said control module incorporates a first and asecond inlet located on separate sides of said housing and a valveconfigured to regulate the intake between said inlets.

In a further subsidiary aspect, said control module incorporates aninternal conduit between said inlet and said outlet; said internalconduit comprising two adjacent paths, one of which incorporates a pumpand a second of which incorporates a non-return valve.

In a further subsidiary aspect, said arrangement further comprises atransportable backup module incorporating one of a heat pump, aninverter, a peltier cooler, or an evaporative cooler; and furtherincorporating means for linking said backup module to said PCM module.

In a third broad independent aspect, a PCM (phase change material) packcomprises a laminate of a first conducting panel and a second conductingpanel enclosing a portion formed primarily of PCM; wherein said portionof PCM incorporates thermal conductors.

In a subsidiary aspect, said thermal conductors extend in a transversedirection from one or both of said conducting panels.

In a further subsidiary aspect, said thermal conductors form hexagonalcells when viewed in plan.

In a further subsidiary aspect, said laminate further incorporates acorrugated thermally conductive panel.

In a further subsidiary aspect, said laminate incorporates a thirdconductive panel and a fourth conductive panel enclosing a secondportion formed primarily of PCM; and a corrugated thermally conductivepanel located between said second and third conductive panels.

In a further subsidiary aspect, said laminate incorporates a pluralityof projections on said panels.

In a further subsidiary aspect, said thermally conductive panels areselected from the group comprising aluminium based material, steel basedmaterial, and plastics material.

In a further subsidiary aspect, said PCM is selected from the groupcomprising a salt, a salt based hydrate, a mixture of salt, and/or saltbased hydrate, and/or an organic material.

In a further subsidiary aspect, said salt based hydrate are selectedfrom the group comprising hydrated calcium chloride or hydrated sodiumsulphate. In a further subsidiary aspect, said salt based hydrateincorporates a thickening agent selected from the group comprisingXanthan and/or Laponite.

In a further subsidiary aspect, said organic material is paraffin based.

In a further subsidiary aspect, said thermal conductors incorporate aconductive compound mixed into said PCM.

In a further subsidiary aspect, said thermal conductor is a carbon basedcompound mixed into said PCM.

In a further subsidiary aspect, said carbon based compound is carbonblack.

In a further subsidiary aspect, said thermal conductors incorporate wirewool or chemical carbon nanotubes.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter withreference to the accompanying drawings, in which:

FIG. 1 shows a fluid conditioning arrangement in schematiccross-sectional view of an embodiment incorporating primarily a PCMmodule and secondarily a heat exchanger unit.

FIG. 2 shows a schematic cross-sectional view of a PCM based fluidconditioning arrangement with a cryogenic booster.

FIG. 3 shows a schematic of a fluid conditioning arrangement where theheat transfer between a first fluid conditioning arrangement and asecond fluid conditioning arrangement is achieved by using fluid insteadof air.

FIG. 4 shows a schematic of the central unit in a fluid conditioningarrangement in accordance with a further embodiment.

FIG. 5 shows a fluid conditioning arrangement incorporating anevaporative unit.

FIG. 6 shows a module which has no PCM material.

FIG. 7 shows a PCM tank.

FIG. 8 shows a PCM module with a fluid based heat exchange.

FIG. 9 shows a further embodiment with a PCM module of the kind shown inFIG. 8.

FIG. 10 shows a control unit.

FIG. 11 shows a PCM module.

FIG. 12 shows a system with a couple of modules.

FIG. 13 shows a Peltiere booster.

FIGS. 14 show PCM packs in a plurality of views.

FIGS. 15 show PCM monoliths in a plurality of views.

FIGS. 16 show a plurality of PCM packs with hexagonal componentsthroughout.

FIGS. 17 shows PCM packs in a plurality of views.

FIGS. 18 show PCM packs with semi-circular troughs in a plurality ofviews.

FIG. 19 shows a heat exchanger in cross section with a plurality of PCMpacks separated by corrugated plates.

FIG. 20 shows an exploded view in a perspective of the embodiment ofFIG. 19.

FIG. 21 shows in perspective view the combination of a PCM pack with acorrugated plate.

FIG. 22 shows in perspective view a portable PCM pack.

FIGS. 23A and B show a PCM pack incorporating a thermally conductivecorrugated plate.

FIG. 24 shows in perspective view the assembly of a PCM pack with acorrugated plate with a plurality of holes.

FIG. 25 shows a perspective view of the assembly of a hexagonal array.

FIG. 26 shows a perspective view of the assembly of a PCM pack with ahexagonal array with perforations.

FIGS. 27A and B show in cross section and in perspective view PCM packsincorporating a corrugated wall.

FIGS. 28A and B show respectively in cross section and in perspective aPCM pack whose envelope may be formed by extrusion.

FIG. 29 shows a perspective view of a heat exchanger incorporating anumber of PCM packs of the kind shown in FIG. 28.

FIG. 30 shows a perspective view of a heat exchanger incorporating anumber of PCM packs of the embodiment of FIGS. 28.

FIG. 31 illustrates a phase change material pack in accordance with theinvention.

FIGS. 32 to 35 show schematically various embodiments of the fluidconditioning system.

DETAILED DESCRIPTION

FIG. 1 shows a fluid conditioning arrangement generally referenced 1.The air conditioning arrangement 1 incorporates three air inletsrespectively referenced 2, 3 and 4. Through inlet 3 fresh air fromoutside is drawn into the housing 5 by a fan or pump 6. It is importantto note that whilst the embodiments of the invention are primarilyillustrated for cooling air, other fluids may also be cooled and/orheated using these systems. In a conventional mode of operation the airis fed through a PCM heat exchanger 7 so that any heat in the air may beabsorbed by the PCM before exiting the housing through outlet 8. Thearrangement may preferably be equipped with a controller which may beconfigured to measure the temperature of the PCM in order to determinethe extent of cooling that may be achieved by the heat exchanger. If dueto the conditions surrounding the heat exchanger, a booster is required,as for example, the PCM heat exchanger fails to be effective or theincoming fluid temperatures are not hot/cold enough, the controllerswitches on the booster. In this configuration, the booster incorporatesa heat pump with a cold heat exchanger and condensation tray 9 locatedin the path of the air to be cooled and a hot heat exchanger 10. Theheat pump would incorporate the necessary compressor and expansion valveor an absorption chiller, desiccant or adsorption cooler. Block 11illustrates its location between hot heat exchanger 10 and cold heatexchanger 9 when cooling. If the booster is provide to heat the air thenheat exchanger 10 is the cool heat exchanger and the hot heat exchangeris heat exchanger 9. If the booster is needed during the day, thecontroller would cause the provision of air flow over the hot heatexchanger and would cause valve 12 to be closed whilst valve 13 would beopened. An additional fan would pump air through inlet 4 when thearrangement would be operating in the booster mode of operation. Valve14 is provided to allow re-circulated air through the arrangement. Valve15 is provided to allow and/or block dependent upon the operator'sselection of the intake of fresh air to the arrangement. Valves 14 and15 can be combined. The invention also envisages systems without thevalves or with fewer valves dependent upon the level of controlrequired. Valve 16 is provided in the outlet to the room. The diagramdoes not show other standard air conditioning components such as airdiffusers.

FIG. 2 shows a fluid conditioning arrangement generally referenced 17with a booster arrangement employing a liquid carbon dioxide or nitrogenstore to provide cooling as it expands in the cold heat exchanger 18.Other than for this booster arrangement, the fluid conditioningarrangement is similar to the arrangement shown and described in detailin FIG. 1. Instead of incorporating an air supply to the hot heatexchanger of the booster, the arrangement incorporates an outlet 20 toallow air back outside. At night, valve 15 opens and valve 14 closes tolet in night air. The controller of the arrangement causes the boosterarrangement to operate if the night air is not cold enough to freeze thePCM. Valve 16 closes and valve 12 opens if the room temperature gets toocold. During the day valve C closes and valve D opens to let air intothe room. If it is cold outside then valve 15 opens and valve 14 closesso less air is re-circulated and vice versa. An escape valve is alsoprovided to allow the expanded gas to escape once the cooling has beentransferred to the heat exchanger.

FIG. 3 shows a further fluid conditioning arrangement generallyreferenced 21, with a central unit 22 incorporating a booster unit 31,and a plurality of PCM units 23, 24 and 25 distributed around the spaceto be heated or cooled. Heat transfer fluid lines are provided such asheat transfer fluid line 26. A return line 27 is provided. When thecontrol unit identifies that the PCM stores which are positioned aroundthe building have failed to deliver the desired cooling effect, thebooster system 31 is switched on. The booster incorporates a heatexchanger, and could be an evaporative, heat pump, vapour compressionsystem, etc. An air intake 29 draws air from outside across the heatexchanger 28 for cooling or heating when the booster is not needed. Avalve 30 is provided between air inlet 29 and optional booster system31. A further air intake 32 allows air into the optional booster systemwhen in use. An air outlet 33 exhausts hot air from the booster ifapplicable; for example if a heat pump is used to provide cooling. Thesystem can work in a number of ways, For example at night cool air viainlet 29, can be passed over heat exchanger 28, and this transferred tothe PCM modules 23,24 and 25 via the separate fluid lines 26 and 27 tofreeze the PCM. If the night time temperature is not cool enough tofreeze the PCM then the booster 31 is turned on and air is passedthrough booster 31 from outside and further cooled by the booster beforepassing over heat exchanger 28. During the day the PCM modules 23,24,25can independently provide cooling to the space as is needed, viaradiation or by passing air over a separate heat exchanger. Ifadditional cooling or heating is needed then the booster system canoperate independently.

FIG. 4 shows a central unit for heating or cooling. This systemincorporates an external solar collector 34 which is in fluidcommunication with a drain-off tank 35 which is configured to preventwater freezing in the solar collector at night. A further fluid line 36is provided between tank 35 and a hot water tank 37. A boiler 38 islocated in series with the hot water tank. The solar collector provideshot water or cooling by working as a radiator at night. During the day,the solar collector provides hot water which can be boosted by theboiler if needed and stored in the hot water tank. Because much of theheat is provided during the day and heating is required at night inresidential buildings, the heat may be stored in the latent heat storesaround the building. In the summer, the system can still store hot waterin the tank for showers but at night cooling from outside can be fed tothe PCM tanks in the room by bypassing the hot water tank.

Instead of employing the central unit of the kind described in FIG. 4,an evaporative central unit generally referenced 39 may be employed asshown in FIG. 5. This unit incorporates housing 40, an air inlet 41equipped with a filter, a single or a multiple stage evaporative coolerwith a wicking mesh 42, an exhaust air outlet 43 and a fan 44 to causethe flow of air through the unit. A first heat transfer line 45 isemployed to return warm water to the unit whilst a heat transfer line 46is employed to allow cold water to circulate to units in the room. Thisconfiguration is particularly advantageous because it allows the workingfluid, i.e. the water from the evaporator to cool the PCM rather thanthe wet air to be used by an evaporative cooler which increases thehumidity of a room.

Instead of, or in addition to, the PCM units of FIG. 3, a unit 47 asshown in FIG. 6 may be employed. This unit may receive and return fluidfrom a central system by heat transfer line inlet 48 and outlet 49.Housing 50 incorporates an air inlet 51 equipped with a filter. An airoutlet 52 is provided at an opposite side of the housing 50. A fan 53draws the air through the unit.

FIG. 7 shows an alternative unit which may be placed in a building andwhich may receive and return fluid from a central system. Unit 54incorporates a housing 55 containing PCM 56. One or more of the sides ofthe unit such as side 57 incorporates no insulation so that coolingand/or heating may be released from these sides by radiation and naturalconvection into the room.

FIG. 8 shows a unit 58 with a housing 59 for containing spaced apart PCMcomponents such as component 60. The unit incorporates an air inlet 61equipped with a filter and an air outlet 62 with a fan 63. The PCMcomponents may be plate-like, spherical, shell-like and tubular heatexchangers etc. A heat transfer line 64 forms a winding pattern in closeproximity to the PCM, or inside the PCM Pack itself in order to optimiseheat transfer. The invention also envisages employing two differentkinds of PCM with different melting temperatures for heating andcooling. The heating range may be 40 to 60° Degrees Celsius whilst thecooling range may be 15 to 32° Celsius.

FIG. 9 shows a further unit generally referenced 65 with a housing 66containing a plurality of PCM components such as component 67. Thehousing 66 incorporates an air intake 68 and an air outlet 69. A valve70 is provided in a duct to regulate whether air is received fromoutside or re-circulated from the room. A further valve 71 is providedto regulate whether the air goes back outside or whether it goes intothe room. When this system is combined with ventilation, it has theadvantage of using a heat transfer fluid line 72 with a higher heatcapacity than air. It is particularly advantageous when used to freezePCM whilst still providing fresh air.

FIG. 10 shows a control unit which may be used to assess therequirements of a system. A valve 73 is provided to determine whetherthe air is re-circulated from the building, taken from outside, or takenfrom a booster. A fan 74 is provided to draw air through the system. Apressure sensor 75 determines the pressure in order to adjust the fanspeed. If the pressure in the duct 76 increases, then the fan is causedto slow down. The pressure sensor may incorporate a pilot tube or anyother component suitable for determining a value which may then beequated to the pressure in the duct.

FIG. 11 shows a further unit generally referenced 77 with a stack of PCMpacks such as pack 78. Unit 77 incorporates a housing 79 for insulatingthe contents of the unit from the outside heat. Dampers or valves 80 areprovided in the inlet duct. A control unit 81 is provided to determinehow much air flows through the unit dependent upon how much cooling isneeded. An operator interface may be provided to adjust the level ofcooling needed.

FIG. 12 shows two rooms 82 and 83, each incorporating a PCM modulerespectively referenced 84 and 85. A duct 86 communicates air to the PCMmodules. A control unit which may be of the kind shown in FIG. 10 isgenerally referenced 87. Upstream from the control unit, a booster unit88 is provided. The booster unit may be of the kind shown in theprevious embodiments. These control and PCM modules can be those ofFIGS. 10 and 11.

The booster may take the form of a Peltier booster which may be of theform shown in FIG. 13 where a unit 89 has a hot side 90 and a cold side91. The cold side 91 incorporates a condensation tray 92 or acondensation catcher 93 in order to allow condensation to run off.

FIG. 14 shows a PCM unit 94 incorporating PCM packs 95. Each packincorporates a plurality of recess portions 96 running the length of thepacks. The PCM packs incorporate PCM material and an appropriatenon-permeable envelope 97. The recesses are formed in the envelope. Therecesses extend only partially across the depth of the packs. Therecesses reduce in width progressively as the depth of the recessincreases. A flat base face 98 is provided at the bottom of each recess.The recess portions allow the circulation of fluid for optimum heatexchanging. FIG. 14B shows the arrangement of Figure A in perspectiveview. FIG. 14 C shows a cross-sectional view of a PCM pack, whilst FIG.14D shows a perspective view of a PCM pack.

FIGS. 15 show a PCM unit 99 with a plurality of hexagonal tubes 100.Each tube contains PCM material and is capped at both ends by a lid 101.By stacking a plurality of hexagonal tubes 100, a number of hexagonalducts 101 are formed which may be used to allow heating fluid tocirculate through the unit.

FIGS. 16 show views of PCM packs. PCM pack 102 with upper and lowersurfaces 103 and 104 which are formed by a succession of recess portionssuch as recessed portion 105 which increases in width from a flat baseportion 106. The recess portions are effectively half of a hexagon.There are provided protrusions 107 which are also effectively half of ahexagon. The PCM pack is formed as if it were formed by a plurality ofside-by-side hexagonal tubes with the common faces such as face 108removed so that the PCM material is distributed throughout the PCM pack.Thermal conductors may be provided between the upper surface 103 and thelower surface 104 in an alternative embodiment. By stacking a pluralityof PCM packs of this form as shown in FIG. 6F channels for circulatingfluid such as channel 109 are formed.

FIGS. 17 show PCM packs incorporating tubes at regular intervalsextending through the PCM layer. Tubes 110 may be used to circulatecooling fluid as appropriate. A cap 111 allows access to the inside ofthe pack for filling the pack with PCM. A second cap 112 is alsoprovided for facilitating the filing and emptying of the PCM pack.

FIGS. 18 show PCM packs in accordance with a further embodiment wherethe pack 113 incorporates a plurality of semi-circular, in crosssection, troughs 114. The recesses or troughs are provided in both theupper surface 115 and the lower surface 116. The troughs in the uppersurface are offset relative to the troughs of the lower surface. Atrough in the upper surface is located opposite a flat outermost portionof the lower surface.

FIG. 19 shows a PCM module in cross-section which takes the form of aheat exchanger 242 with an insulative housing 243. The housing wall maybe selected to hold 80 to 90% of the “coolth” over 8 hours. It may be ofapproximately 25 mm in thickness with a conductivity of 0.01 to 0.02W/MK. On the inside of housing 243, a conductive metal frame 244 forms alining. A succession of layers of corrugated plates such as plate 45alternate with PCM pack layers such as layer 246. FIG. 20 shows thecomponents of FIG. 19 in an exploded view. The corrugated plate mayinstead be replaced by a number of transverse fins or links which in asimilar fashion as the corrugated plate would increase the surface areain contact with air flowing through the channels left between the PCMpacks. Since the surface area in contact with air is increased, the PCMpacks may be thicker thus allowing greater cooling to be achieved. In apreferred embodiment, the gap between the PCM packs is slightly smallerthan the height of the corrugated fins to ensure optimum thermalcontact. In order to support the weight of the PCM packs, there isprovided rails on the inside of the frame (not shown in the figures).FIG. 21 shows a corrugated plate 247 with a number of projections suchas projection 248. Alternatively, these projections may be holes or acombination of holes and projections in order to break up laminar flowby creating turbulence in order to increase heat transfer. Thecorrugated plate 247 may be disposed as shown in FIG. 19 adjacent to asealed PCM pack 249. The corrugated plate 247 may preferably be made ofsheet metal preferably less than 1 mm thick. For optimum structuralstrength and thermal conductivity, a range of 0.1 to 0.2 mm isenvisaged. A number of known techniques are envisaged to form the platesuch as pressing or folding. Instead of employing sheet metal, athermally conductive plastics material may also be selected.

FIG. 22 shows a PCM pack 250 with an impermeable outer layer 251 forcontaining the PCM. A handle 252 is provided which may take the form ofan oblong opening. A number of recesses 253 and 254 are provided onopposite lateral sides of the pack. These may be employed in order tolock the pack into releasable attachment means provided in a heatexchanger for example. This embodiment illustrates how the PCM pack maybe rendered readily portable.

FIG. 23A shows a PCM pack formed with an upper wall 255 and a lower wall256 for trapping PCM. Between walls 255 and 256, there is provided aplate 257 formed as a succession of V-shaped portions when viewed incross-section. The components of FIG. 23A are shown in FIG. 23B as gluedor sealed together in order to prevent any escape of PCM during use.

The PCM is one of an organic, a salt based hydrate, or a combination ofboth. A paraffin based PCM is envisaged with a melt temperaturepreferably within the range of 21 to 24 degrees Celsius. In order toachieve an optimal melt temperature, the different types of availableparaffins are mixed in the appropriate proportions.

Salt hydrates which are suitable for use may for example be hydratedforms of calcium chloride or sodium sulphate. The invention alsoenvisages employing a thickening agent as an addition to the salthydrates to maintain the salt in its hydrated form. Suitable thickeningagents may be selected from the group comprising: Xanthan or Laponite.In addition to the transverse conductive fins of the corrugated plate257 or instead of such transverse fins, a conductive element may besuspended in the mixture of PCM. An appropriate compound for suspensionmay be carbon black.

FIG. 24 shows an alternative construction of a PCM pack generallyreferenced 258. The configuration of the PCM pack differs from thepreceding embodiment in that a number of holes 259 are provided in thefins 260 of the corrugated plate generally referenced 261. Such holesallow molten PCM to distribute evenly and to keep air out. Thecorrugated panel may be glued to improve strength.

The corrugated panels may be pressed and mainly made of very thin wallthicknesses such as less than 1 mm in order to keep weight to a minimumwhilst the profile/ridges/pattern adds a strength. The transverse finsallow the thickness of the PCM pack to be increased by improvingconductivity. It allows the PCM to be at an optimal maximum distance ofbetween 4 to 16 mm (or 10 to 20 mm) from the links throughout the pack.Alternative thermal conductors are envisaged to be located in the PCMsuch as wire wool, chemical carbon nano-tubes, suspended carbon blackwhich may be randomly distributed throughout the material.

The transverse links may be made of thin metal/plastic which wouldpreferably be less than 1 mm in thickness. The shape and configurationof the plate may be obtained by pressing, stamping and/or foldingprocesses.

FIG. 25 shows a PCM pack 262 in an exploded view with an array ofclosely contiguous cylinders 263 for receiving PCM. The cylindricaltubes may take the form of a hexagonal mesh. The array may be formedfrom a single sheet which is laser cut and pulled apart to result in anarray with walls of a thickness of approximately 0.1 mms. Secured to thetop and bottom of the array, there is provided top and bottom platesrespectively referenced 264 and 265. The process of assembling mayincorporate the following steps: a) attaching the array of hexagonalreceptacles to one of the top or bottom plates, b) filling the tubeswith PCM in its molten phase allowing sufficient clearance for itsexpansion as it freezes before c) gluing to attach the remaining panel.

An alternative PCM pack 266 is shown when compared to the embodiment ofFIG. 25. PCM pack 266 incorporates a shallow walled plateau 267 intowhich an array of hexagonal receptacles 268 is located. The array ofreceptacles is sealed between lid 269 and plateau 267. Holes such ashole 270 are provided through each of the hexagonal receptacles in orderto allow PCM to distribute. The panel 269 may be attached to the plateau267 by ultrasonic welding or by gluing.

If the PCM is selected to be salt based the material for the pack ispreferably selected to be a coated aluminium or a conductive plasticsmaterial (for example K greater than 5 W/MK) or stainless steel in orderto prevent corrosion.

One of the key advantages of transverse links is that it allows PCMpacks to be made of a greater thickness than would otherwise bepossible. For example packs with material thicknesses of 20 to 50 mm maybe achieved with effective conductivity.

FIGS. 27A and 27B a PCM pack (FIG. 27A) and a stack of PCM packs (FIG.27B). In this embodiment, the PCM pack is generally referenced 271 andis formed only of two plates 272 and 273 allowing for the filling of PCMin an array of cavities such as cavity 274. The cavities are formed incross-section in a V-shape. The portions such as portion 275 would beexposed to air flow. In addition, it is envisaged for the externalsurface exposed to the flow to incorporate knurling and/or bumps. Thiskind of relief may be used in any of the preceding embodiments in orderto increase the flow turbulence and therefore the heat transferproperties of the pack. The undulated or corrugated plate 273 is formedfor example by pressing or folding. As indicated in the stack of packs276 and 277 air may flow in the cavities provided as indicated by thearrows. This embodiment allows an increase in surface area in contactwith the air and a reduction of the maximum distance between the PCM andthe conductive material. In other words, it combines the function f thePCM packaging with the transverse links inside as well as the corrugatedheat exchanger in touch with the air.

FIGS. 28A and 28B show a PCM pack 278 in two separate views. The PCMpacks 278 incorporate a single peripheral wall 279 with a number ofinwardly projecting webs such as web 280 and outwardly projecting webssuch as web 281. In other embodiments only externally projecting websmay be provided and/or only internally projecting webs. Within theenvelope formed by peripheral wall 279, PCM 282 is placed to fill thespace. In order to enclose the PCM pack, end pieces (not shown in thefigures) may be provided and secured onto lateral edges 283 and 284. Thematerials used for these PCM packs may be a relatively low permeableplastics material. Alternatively, coated aluminium is also advantageous.Preferably, a conductive of plastics material would be selected with athermal conductivity factor greater than 1 W/MK. An option of achievingthis kind of conductive of plastics material for the PCM pack materialwould be to add carbon nano-tubes or particles to the plastics material.The process envisaged in order to produce wall 279 would be to form thewall by extrusion.

FIG. 29 shows a PCM pack module generally referenced 285. Module 285incorporates an insulative outer layer 286 formed by side walls 287,288, a base wall 289 and a lid 290. Within the insulation, there isprovided a frame 291 with a number of ledges such as ledge 292 forsupporting a stack of PCM packs in a spaced apart relationship. Gapssuch as gap 93 are provided to allow the circulation of fluid. The links280 and 281 extend in this embodiment only partially towards aneighbouring PCM pack plate.

As shown in FIG. 30, during assembly, a side 294 may be fully open inorder to allow the insertion of the successive packs in similar fashionto a drawer sliding into its case.

FIG. 31 shows a phase change material pack 300 according to anembodiment of the invention. The pack is made from two pressed panels301 which are joined at their edges and at two locations 302 in themiddle of the pack surface for strength. The surface of the pack istextured to induce turbulent flow in the fluid (air) passing over it.

A conductive PCM material allows the PCM packs to be thicker, reducingmanufacturing costs. Currently the PCM packs/panels are 10-15 mm thick.Where salt based hydrates are used then the pack material must benon-corrosive, non-permeable and robust. Preferably, depending on thethickness, the material should be thermally conductive.

Preferably metals are used to form the panels 301 as they arenon-permeable and highly conductive. Those with the best corrosiveproperties are aluminium and stainless steel. Further coatings may beneeded to reduce the effects of corrosion depending on the salt.Suitable techniques are anodizing, E-Coat or Electro Coat, silanecoating, PTFE. Depending on the method of manufacture there are manyprocesses which allow the protective layer to form naturally during themanufacturing process. Aluminium alloys 5052 & 5251 have goodformability and very good corrosion resistance, reducing the need forthe level of coatings.

Many plastics have poor permeability and their mechanical propertiesdegrade over time due to the effects of the salt hydrate weakening theplastic, this means that plastics generally need higher wall thickness,ie 1-5 mm rather than 0-1 mm with metals. HDPE is one of the best offthe shelf plastics. Additives/processes used to make plastics moreconductive also have a positive effect on plastics permeability.

A composite material may be used. As used commonly in the food industrythis may consist of a film of a number of different materials, e.g.aluminium foil for permeability reasons, plastic for corrosive reasons.

The typical method of manufacture is using superforming/hydroforming orstamping two sides of the pack, and then epoxy gluing or welding theedges shut. A preferably resealable opening is left to fill/refill thepack.

The methods to control the selective operation of the secondary heatexchanger will now be described. Temperature sensors are placed outside,or within a duct in which outside air enters the building, and insidethe area to be serviced by the system. Depending on the requiredtemperature inside the system can provide ventilation, free cooling orcooling/heating via the latent heat store. For example if it is colderoutside than inside and cooling is needed, the system can provide directventilation bypassing the latent heat store to cool the room. This savesthe latent heat store until it is needed. If it is warmer outside thaninside then the proportion of outside air to re-circulated air isdetermined by the minimal ventilation requirements, and the latent heatstore is used to cool the air.

The latent heat store is recharged by passing cool night time airthrough the system, and either dumping the air in the room (with thebenefit of cooling the room) or outside (if the room is occupied and indanger of being over cooled).

In winter the system traps excess heat at the end of the day, or duringpeak heating periods (e.g. when the sun hits a glass frontedbuilding—even in winter overheating can occur in these situations) andthis is used to temper the ventilated air.

An optional humidity sensor(s) may monitor the outside humidity andhumidity inside, in order to ensure the internal environment does notfall outside the optimum range of 30-70%. For example when raining or itis very humid outside, less ventilation may be provided in order toprevent the humidity rises above these parameters.

An optional CO2 or other pollutant sensor may be provided to monitorindoor air quality and used to control the amount of freshair/ventilation provided to the space. Alternatively infra red, motionor proximity sensors may be used to detect occupants or the number ofoccupants. This is advantageous when the area to be serviced has avariable number of occupants, or usage and therefore the ventilationrate can be varied to better serve the occupants and/or save energy.

Contacts can be placed inside the pack, and the electrical resistanceacross the phase change material can be measured. The resistance changesas the PCM melts or solidifies. Care needs to be taken that the packdoes not ‘short’ the measurement circuit.

A temperature sensor can be used inside the pack to measure thetemperature of the PCM itself or placed on the surface of the pack tomeasure the outside temperature of the pack. One potential problem withboth this method and the previous one is that they only measure in asingle location, and may result in localised effects, or they requiremultiple sensors. The sensors also have to be able to be disconnected asthe packs are removable.

With either of these methods the system can monitor the state of thePCM. If the PCM does not reach the desired temperature after a certaintime, e.g. when cooling at night, then the control system will turn thebooster on.

Typically a temperature sensor and preferably a humidity sensor areplaced at the start and end of the PCM heat exchanger. An algorithm canthen be used to calculate the state of the PCM and whether the boosteris needed.

The power output of the heat exchanger is governed by the followingequation:

P=ρ.v.c.h(ΔT)

P—power (KW or KJ/s)

ρ—density of air or HT fluid (˜1.2 Kg/m³)

v—volume flow rate (m³/s)

h—heat exchanger efficiency (%)

ΔT—difference in temperature between start and end of heat exchanger

The flow rate can be determined by the control system from the fan speedand whether the air is recirculated/mixed or pulled in from outside (asthe resistance will change). Apart from the temperatures the othervariables are constant.

If the temperature of the air out of the heat exchanger is greater thana certain value, e.g. 18 C then the PCM needs further cooling. Thesystem knows the total energy stored in the PCM (from the latent heatKJ/KG and the mass of PCM), and the rate that the system is rechargingthe PCM based on the equation above. If the temperature differencebetween the air in and air out of the heat exchanger is small, or if thesystem calculates that the recharge rate will not freeze all the PCM inthe given time period (e.g. 6 hours overnight), then the system canincrease the air flow via the fan speed to get the required rechargerate, or turn on the booster system to lower the temperature of the airentering the heat exchanger. When the temperature difference between theair entering the heat exchanger and leaving it is small, then the systemknows that no further recharging is possible unless the outsidetemperature drops further (in which case the fan speed can be turneddown/off to save energy) or the booster is turned on to drop thetemperature further. The system may also take into account approximate

In a similar way the system can calculate whether the current rate ofcooling will mean the system will run out of cooling before the end ofthe day, and therefore turn the booster on, increase or decrease the airflow rate.

FIG. 32 show an embodiment of the fluid conditioning apparatus in whichthe secondary heat exchanger can be bypassed when not in use, so thatenergy is not wasted when the secondary heat exchanger is not in use. Inthis embodiment, air from outside the building enters the system througha first filter 401. Air from the room to be heated/cooled enters througha second filter 402. A valve 403 selects the proportion of air fromoutside and from within the room that is supplied to the fan 404 andthrough the PCM heat exchanger 405. A second valve 406 selects theproportion of air that is returned to the outside or back to the roomafter passing through the PCM heat exchanger.

An evaporator and secondary heat exchanger 407 is provided in the pathof the air from the first valve 403. A bypass valve 408 selects whetherthe incoming air passes through the secondary heat exchanger or not. Acondenser air conditioning unit 409, usually located outside thebuilding comprises a condenser 410 and a compressor 411. Any chillerunit could be used. An expansion valve 412 is provided in the upstreampath from the air conditioning unit 409.

FIG. 33 shows a further version of the fluid conditioning apparatus inwhich the same reference numerals are used for the same components shownin FIG. 32. In FIG. 33, an indirect evaporator 413 is provided toseparate the wet side of the system from the air entering the controlledenvironment so that there is no increase in humidity in the controlledenvironment. The evaporator 413 may be located remotely. In thisembodiment the first valve 403 acts as a bypass valve 408.

FIG. 34 shows a further version of the fluid conditioning apparatus inwhich the same reference numerals are used for the same components shownin FIGS. 32 and 33. In this embodiment, a remote booster unit 415, whichmay use any suitable heat exchanger is connected to the PCM heatexchanger 405 via an input duct 416. An exhaust duct 417 is provided tothe outside environment. In FIG. 34, the outside perimeter of the roomto be serviced is indicated by reference number 418. A weather louvre419 is provided with an additional fan 420 for pulling air out of theroom 418 so that the load on the main fan 404 is reduced.

FIG. 35 shows a further version of the fluid conditioning apparatus inwhich the same reference numerals are used for the same components asthe preceding figures. In FIG. 35, the dashed lines show how the systemcan be divided up into a control unit module 421, a bypass module 422and a booster module 423 connected by appropriate ducting. The boostermodule 423 can also be placed between the control module 421 and the PCMheat exchanger 405.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of them mean “including but notlimited to”, and they are not intended to (and do not) exclude othermoieties, additives, components, integers or steps. Throughout thedescription and claims of this specification, the singular encompassesthe plural unless the context otherwise requires. In particular, wherethe indefinite article is used, the specification is to be understood ascontemplating plurality as well as singularity, unless the contextrequires otherwise.

Features, integers or characteristics described in conjunction with aparticular aspect, embodiment or example of the invention are to beunderstood to be applicable to any other aspect, embodiment or exampledescribed herein unless incompatible therewith. All of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), and/or all of the steps of any method or processso disclosed, may be combined in any combination, except combinationswhere at least some of such features and/or steps are mutuallyexclusive. The invention is not restricted to the details of anyforegoing embodiments. The invention extends to any novel one, or anynovel combination, of the features disclosed in this specification(including any accompanying claims, abstract and drawings), or to anynovel one, or any novel combination, of the steps of any method orprocess so disclosed.

1. A fluid conditioning arrangement comprising a primary heat exchangerconfigured to cool and/or heat the fluid; a secondary heat exchangerconfigured to cool and/or heat the fluid; and a controller for operatingsaid secondary heat exchanger when said primary heat exchanger fails tocool and/or heat the fluid at a predetermined acceptable level; whereinsaid primary heat exchanger is a phase change material (PCM) based heatexchanger.
 2. An arrangement according to claim 1, wherein saidsecondary heat exchanger is selected from: a vapour compression cyclebased air conditioning system, a heat pump, an absorption chiller, adesiccant, an adsorption cooler or a heater element.
 3. An arrangementaccording to claim 1, wherein said secondary heat exchanger incorporatesa liquid store suitable for cryogenic cooling.
 4. An arrangementaccording to claim 1, wherein said secondary heat exchanger incorporatesan evaporative cooler.
 5. An arrangement according to claim 4, whereinsaid evaporative cooler incorporates a housing with an air intake; acorresponding air outlet; a liquid inlet; a corresponding liquid outlet;and a wicking surface.
 6. An arrangement according to claim 1, whereinsaid secondary heat exchanger incorporates a Peltier cooler.
 7. Anarrangement according to claim 1, wherein said secondary heat exchangerexchanges heat with a liquid which then exchanges heat with the PCM ofsaid primary heat exchanger.
 8. An arrangement according to claim 1,wherein said primary heat exchanger incorporates one or more unitshousing PCM; wherein said housing incorporates a PCM tank.
 9. Anarrangement according to claim 8, wherein said tank incorporatesinsulated sides and at least one side without insulation in order toenhance convection through said side.
 10. A phase change material (PCM)module comprising a number of PCM packs; a housing for thermallyinsulating said number of PCM packs from a module's surrounding medium;said packs being in the form of a panel with an upper surface, a lowersurface, and relatively narrow lateral sides; wherein a plurality oftroughs in at least either the upper or lower surfaces of the panel areprovided to allow fluid to flow through the module for heat exchangewith the PCM.
 11. A phase change material (PCM) module comprising anumber of PCM monoliths; a housing for thermally insulating said numberof PCM monoliths from a module's surrounding medium; and gaps beingformed between a stack of said monoliths in said module to allow fluidto flow through the module for heat exchange with the PCM.
 12. A moduleaccording to claim 11, wherein said monoliths are hexagonal incross-section.
 13. A phase change material (PCM) module comprising anumber of PCM packs; a housing for thermally insulating said number ofPCM packs from a module's surrounding medium; and conduits passingthrough said PCM packs to allow fluid to flow through the module forheat exchange with the PCM.
 14. A fluid conditioning arrangementcomprising a first heat exchanger configured to cool and/or heat fluid;and a second heat exchanger configured to cool and/or heat fluid;wherein said one of said heat exchangers is a phase change material(PCM) based heat exchanger; and the other is an evaporative cooler. 15.A fluid conditioning arrangement comprising a first heat exchangerconfigured to cool and/or heat fluid; and a second heat exchangerconfigured to cool and/or heat fluid; wherein said one of said heatexchangers is a phase change material (PCM) based heat exchanger; andthe other is a Peltier cooler.
 16. A fluid conditioning arrangementcomprising a first heat exchanger configured to cool and/or heat fluid;and a second heat exchanger configured to cool and/or heat fluid;wherein said one of said heat exchangers is a phase change material(PCM) based heat exchanger; and the other is a solar based heatexchanger.
 17. (canceled)